In general, a linearly polarized (LP) wave can be changed into an elliptically (EP) polarized or circularly polarized (CP) wave by using a wave polarizer. Therefore, it is theoretically possible to obtain an EP or CP antenna by adding a wave polarizer to an LP antenna. However, adding an external polarizer inevitably increases the size and complexity of the resulting antenna which is not desirable.
M. Ikeda, H. Nakano, “Antenna for receiving circularly polarized wave,” JP3848603 (B2), 22 Nov. 2006 discloses an antenna for receiving circularly polarized waves. The antenna comprises a monopole antenna having a pole part and an earth plate for grounding one terminal of the pole part, and a polarization conversion means arranged around the monopole antenna. The polarization conversion means consists of a plurality of helical conductors which are spaced from the pole part by a prescribed distance and are helically wound around the pole part and have one end grounded to the earth plate. The helical conductors are arranged around the pole part at uniform angular intervals. This is a complex structure to manufacture.
J. L. Schadler, “Circularly polarized low wind load omnidirectional antenna apparatus and method,” U.S. Pat. No. 7,649,505 (B2), 19 Jan. 2010 discloses a circularly polarized, omnidirectional, corporate-feed pylon antenna using multiple helically-oriented dipoles in each bay, and including a vertical and diagonal support arrangement of simple structural shapes configured to provide a frame strong enough to sustain mechanical top loads applied externally. The radiators in each bay fit within the vertical supports. The radiators are integrally formed with cross-braces, and are fed with manifold feed straps incorporating tuning paddles. A single cylindrical radome surrounds the radiative parts and the vertical supports. This is also a complex structure to manufacture.
M. Takahashi, “Antenna,” JP9232835 (A), 5 Sep. 1997 discloses an antenna structure for a mobile telephone radio communication system base station. The antenna has an outer sheath on a surface of a support pole. Slots corresponding to the operating frequency of the radio communication system are made in the outer sheath and act like a radio wave radiation means. The support pole and the outer sheath are energized by a feeding means from the base station. The radio wave from the base station is radiated uniformly from the slots formed in the outer sheath. This antenna structure is limited to large size antennas for base stations or the like.
None of the three foregoing antenna structures employs a dielectric resonator or dielectric block.
T. H. Chang, J. F. Kiang, “Circularly-polarized dielectric resonator antenna,” U.S. Pat. No. 7,541,998 (B1), 2 Jun. 2009 discloses a circularly-polarized dielectric resonator antenna (DRA). The antenna comprises a substrate, a Wilkinson power divider, a phase shifter, a ground plane and a dielectric resonator, wherein the phase shifter is connected to the Wilkinson power divider. The dielectric resonator is disposed on the ground plane, and includes a dielectric main body and a slot disposed above the substrate. Additionally, the antenna is adopted to increase the linear radiation bandwidth by utilizing the slot, and transceives a circularly-polarized electromagnetic wave by utilizing the Wilkinson power divider.
M. B. Oliver, Y. M. M. Antar, “Broadband circularly polarized dielectric resonator antenna,” U.S. Pat. No. 5,940,036 (A), 17 Aug. 1999 discloses a radiating antenna capable of generating or receiving circularly polarized radiation using a single feed and a dielectric resonator. The dielectric resonator has slightly differing dimensions along two axes. Substantially polarized radiation can be generated in each of two mutually orthogonal modes by placement of the probe at each of two locations. When the feed is situated substantially between these two locations, two orthogonal modes are excited simultaneously.
C. H. Tsao, Y. Hwang, F. J. Kilburg, F. J. Dietrich, “Planar dual polarization antenna,” U.S. Pat. No. 4,903,033 (A), 20 Feb. 1990 discloses a microwave-frequency microstrip antenna simultaneously usable for both transmitting and receiving microwave-frequency signals that have dual orthogonally polarized components. The components may be either linearly or circularly polarized. A radiating patch is mounted on a first dielectric. A ground plane abuts the first dielectric and has two elongated coupling apertures at right angles to each other. A second dielectric abuts the ground plane and has embedded thereon two substantially identical conductive planar feed networks that are disposed at right angles to each other. At least one additional optional dielectric layer having a conductive patch may be interposed between the first dielectric and the ground plane for purposes of broadening the bandwidth of the antenna. A meanderline polarizer or a 3 dB 90 DEG hybrid coupler may be used for converting from linear polarization to circular polarization.
T. M. Smith, “Multifunction antenna assembly with radiating horns,” U.S. Pat. No. 5,596,338, 21 Jan. 1997 discloses an assembly of antenna elements mounted in a unitary structure for transport on a satellite encircling the earth. Each element comprises a horn shaped radiator with opposed arcuate sidewalls, a rectangular waveguide feed, and a transition interconnecting the feed to a throat of the horn. The assembly services a plurality of portions of a communication band within the electromagnetic spectrum. The throats of respective horns are dimensioned for specific frequencies of the respective portions of the communication bands. The antenna elements may provide telemetry and control functions for the satellite. A side-by-side arrangement of the horns permits use of a common meanderline polarizer for conversion of a linearly polarized wave to a circularly polarized wave for each antenna element.
Of the latter four references, U.S. Pat. No. 7,541,998 and U.S. Pat. No. 5,940,036 utilize dielectric elements, but they can generate broadside radiation only, whereas U.S. Pat. No. 4,903,033 and U.S. Pat. No. 5,596,338 put an external polarizer around an LP antenna to achieve the CP radiation, at the cost of substantially increasing the overall antenna size.
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